Selective bifunctional multimetallic reforming catalyst

ABSTRACT

A novel catalyst and the use thereof in a reforming process is disclosed. The catalyst comprises a refractory inorganic oxide, platinum-group metal, Group IVA(IUPAC 14) metal, indium and lanthanide-series metal. Utilization of this catalyst in the conversion of hydrocarbons, especially in reforming, results in significantly improved selectivity to the desired gasoline or aromatics product.

This application is a continuation-in-part of prior copendingapplication Ser. No. 08/762,620 filed Dec. 9, 1996, now issued as U.S.Pat. No. 6,013,173, the contents of which are incorporated herein byreference.

FIELD OF THE INVENTION

This invention relates to an improved catalyst for the conversion ofhydrocarbons, and more specifically for the catalytic reforming ofgasoline-range hydrocarbons.

BACKGROUND OF THE INVENTION

The subject of the present invention is a novel dual-function catalyticcomposite, characterized by a combination of three or more metals inspecified concentrations on the finished catalyst, and its use inhydrocarbon conversion. Catalysts having both ahydrogenation-dehydrogenation function and a cracking function are usedwidely in many applications, particularly in the petroleum andpetrochemical industry, to accelerate a wide spectrum ofhydrocarbon-conversion reactions. The cracking function generallyrelates to an acid-action material of the porous, adsorptive,refractory-oxide type which is typically utilized as the support orcarrier for a heavy-metal component, such as the Group VIII(IUPAC 8-10)metals, which primarily contribute the hydrogenation-dehydrogenationfunction. Other metals in combined or elemental form can influence oneor both of the cracking and hydrogenation-dehydrogenation functions.

In another aspect, the present invention comprehends improved processesthat emanate from the use of the novel catalyst. These dual-functioncatalysts are used to accelerate a wide variety ofhydrocarbon-conversion reactions such as dehydrogenation, hydrogenation,hydrocracking, hydrogenolysis, isomerization, desulfurization,cyclization, alkylation, polymerization, cracking, andhydroisomerization. In a specific aspect, an improved reforming processutilizes the subject catalyst to increase selectivity to gasoline andaromatics products.

Catalytic reforming involves a number of competing processes or reactionsequences. These include dehydrogenation of cyclohexanes to aromatics,dehydroisomerization of alkylcyclopentanes to aromatics,dehydrocyclization of an acyclic hydrocarbon to aromatics, hydrocrackingof paraffins to light products boiling outside the gasoline range,dealkylation of alkylbenzenes and isomerization of paraffins. Some ofthe reactions occurring during reforming, such as hydrocracking whichproduces light paraffin gases, have a deleterious effect on the yield ofproducts boiling in the gasoline range. Process improvements incatalytic reforming thus are targeted toward enhancing those reactionseffecting a higher yield of the gasoline fraction at a given octanenumber.

It is of critical importance that a dual-function catalyst exhibit thecapability both to initially perform its specified functions efficientlyand to perform them satisfactorily for prolonged periods of time. Theparameters used in the art to measure how well a particular catalystperforms its intended functions in a particular hydrocarbon reactionenvironment are activity, selectivity and stability. In a reformingenvironment, these parameters are defined as follows:

1) Activity is a measure of the ability of the catalyst to converthydrocarbon reactants to products at a designated severity level, withseverity level representing a combination of reaction conditions:temperature, pressure, contact time, and hydrogen partial pressure.Activity typically is designated as the octane number of the pentanesand heavier (“C₅+”) product stream from a given feedstock at a givenseverity level, or conversely as the temperature required to achieve agiven octane number.

2) Selectivity refers to the percentage yield of petrochemical aromaticsor C₅+ gasoline product from a given feedstock at a particular activitylevel.

3) Stability refers to the rate of change of activity or selectivity perunit of time or of feedstock processed. Activity stability generally ismeasured as the rate of change of operating temperature per unit of timeor of feedstock to achieve a given C₅+ product octane, with a lower rateof temperature change corresponding to better activity stability, sincecatalytic reforming units typically operate at relatively constantproduct octane. Selectivity stability is measured as the rate ofdecrease of C₅+ product or aromatics yield per unit of time or offeedstock.

Programs to improve performance of reforming catalysts are beingstimulated by the reformulation of gasoline, following upon widespreadremoval of lead anti-knock additive, in order to reduce harmful vehicleemissions. Gasoline upgrading processes such as catalytic reforming mustoperate at higher efficiency with greater flexibility in order to meetthese changing requirements. Catalyst selectivity is becoming ever moreimportant to tailor gasoline components to these needs while avoidinglosses to lower-value products. The major problem facing workers in thisarea of the art, therefore, is to develop more selective catalysts whilemaintaining effective catalyst activity and stability.

The art teaches a variety of multimetallic catalysts for the catalyticreforming of naphtha feedstocks. Most of these comprise combinations ofplatinum-group metals with rhenium and/or Group IVA(IUPAC 14) metals.

U.S. Pat. No. 3,951,868 (Wilhelm) teaches a catalyst comprisingplatinum, halogen, germanium or tin, and indium, wherein the ratio ofindium to platinum-group metal is about 0.1-1:1. U.S. Pat. No. 4,522,935(Robinson et al.) discloses a catalyst comprising a platinum-groupmetal, tin, indium, halogen, and a porous support which may comprisealumina. The feature of the catalyst is an atomic ratio of indium toplatinum-group metal of more than 1.35, and preferably about 2.55.

U.S. Pat. No. 3,915,845 (Antos) discloses hydrocarbon conversion with acatalyst comprising a platinum-group metal, Group IVA metal, halogen andlanthanide in an atomic ratio to platinum-group metal of 0.1 to 1.25.The preferred lanthanides are lanthanum, cerium, and especiallyneodymium which was exemplified in Antos. U.S. Pat. No. 4,039,477(Engelhard et al.) discloses a catalyst for the catalytic hydrotreatmentof hydrocarbons comprising a refractory metal oxide, platinum-groupmetal, tin and at least one metal from yttrium, thorium, uranium,praseodymium, cerium, lanthanum, neodymium, samarium, dysprosium andgadolinium with favorable results being observed at relatively lowratios of the latter metals to platinum.

Another type of multimetallic catalyst has been disclosed as comprisinga combination of platinum with rhodium or osmium and a third metal. U.S.Pat. No. 4,401,557 (Juguin et al.) discloses a reforming process using acatalyst comprising a carrier, platinum, a second metal of eitherrhodium or osmium, and a third metal from the list of chromium,tungsten, molybdenum, manganese, rhenium, gallium, indium, thallium,samarium, zinc, cadmium, titanium, and zirconium. The examples appear toshow that the preferred third metals are essentially tungsten,manganese, rhenium, gallium, germanium, tin, thorium, cerium, andsamarium.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a novel catalyst forimproved selectivity in hydrocarbon conversion. A corollary object ofthe invention is to provide a reforming process having improvedselectivity with respect to gasoline or aromatics yields.

The invention originates from the discovery that a catalyst containingplatinum, tin, indium and cerium on chlorided alumina shows a favorableratio of aromatization to cracking in a reforming reaction.

A broad embodiment of the present invention is a catalyst comprising arefractory inorganic oxide, a platinum-group. metal, a Group IVA(IUPAC14) metal, indium and a lanthanide-series metal. The atomic ratio of thecombination of indium and lanthanide metal to platinum-group metalpreferably is at least about 1.5, more preferably at least about 2. Thecatalyst optimally also comprises a halogen, especially chlorine. Inpreferred embodiments the refractory inorganic oxide is alumina, theplatinum-group metal is platinum, the Group IVA(IUPAC 14) metal is tin,and the lanthanide-series metal is cerium. A highly preferred catalystconsists essentially of platinum, tin, indium and cerium on ahalogenated alumina support.

In another aspect, the invention is a process for the conversion of ahydrocarbon feedstock utilizing a catalyst comprising a refractoryinorganic oxide, a platinum-group metal, a Group IVA(IUPAC 14) metal,indium and a lanthanide-series metal. Preferably the hydrocarbonconversion is catalytic reforming of a naphtha feedstock, utilizing thecatalyst of the invention to increase the yield of gasoline and/oraromatics. The conversion optimally comprises dehydrocyclization toincrease aromatics yields. In an advantageous embodiment, the naphthafeedstock comprises hydrocarbons in the C₆-C₈ range which yield one ormore of benzene, toluene and xylenes in a catalytic reforming unit.

These as well as other objects and embodiments will become evident fromthe following more detailed description of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows conversion of heptanes as a function of temperature usingcatalysts of the prior art and of the present invention.

FIG. 2 compares selectivity to aromatics for catalysts of the prior artand of the present invention when processing a heptane+xylene feedstock.

FIG. 3 shows conversion of paraffin plus naphthene as a function oftemperature using a catalyst of the prior art and of the presentinvention when processing a naphtha feedstock.

FIG. 4 compares selectivity to aromatics for a catalyst of the prior artand of the present invention when processing a naphtha feedstock.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A broad embodiment of the present invention, therefore, is a catalystcomprising a refractory inorganic-oxide support, a platinum-group metal,at least one metal of Group IVA(IUPAC 14) of the Periodic Table [SeeCotton and Wilkinson, Advanced Inorganic Chemistry, John Wiley & Sons(Fifth Edition, 1988)], indium, and a lanthanide-series metal,preferably in combination with a halogen.

The refractory support utilized in the present invention usually is aporous, adsorptive, high-surface area support having a surface area ofabout 25 to about 500 m²/g. The porous carrier material should also beuniform in composition and relatively refractory to the conditionsutilized in the hydrocarbon conversion process. By the terms “uniform incomposition” it is meant that the support be unlayered, has noconcentration gradients of the species inherent to its composition, andis completely homogeneous in composition. Thus, if the support is amixture of two or more refractory materials, the relative amounts ofthese materials will be constant and uniform throughout the entiresupport. Included within the scope of the present invention carrier arematerials which have traditionally been utilized in dual-functionhydrocarbon conversion catalysts such as:

1) refractory inorganic oxides such as alumina, magnesia, titania,zirconia, chromia, zinc oxide, thoria, boria, silica-alumina,silica-magnesia, chromia-alumina, alumina-boria, silica-zirconia, etc.;

2) ceramics, porcelain, bauxite;

3) silica or silica gel, silicon carbide, clays and silicates which aresynthetically prepared or naturally occurring, which may or may not beacid treated, for example attapulgus clay, diatomaceous earth, fuller'searth, kaolin, or kieselguhr;

4) crystalline zeolitic aluminosilicates, such as X-zeolite, Y-zeolite,mordenite, β-zeolite, Ω-zeolite or L-zeolite, either in hydrogen form orpreferably in nonacidic form with one or more alkali metals occupyingthe cationic exchangeable sites;

5) non-zeolitic molecular sieves, such as aluminophosphates orsilico-alumino-phosphates; and

6) combinations of two or more materials from one or more of thesegroups.

Preferably the refractory support comprises one or more inorganicoxides, with the preferred refractory inorganic oxide for use in thepresent invention being alumina. Suitable alumina materials are thecrystalline aluminas known as the gamma-, eta-, and theta-alumina, withgamma- or eta-alumina giving best results. The preferred refractoryinorganic oxide will have an apparent bulk density of about 0.3 to about1.0 g/cc and surface area characteristics such that the average porediameter is about 20 to 300 angstroms, the pore volume is about 0.1 toabout 1 cc/g, and the surface area is about 100 to about 500 m²/g.

Considering that alumina is the preferred refractory inorganic oxide, aparticularly preferred alumina is that which has been characterized inU.S. Pat. Nos. 3,852,190 and 4,012,313 as a by-product from a Zieglerhigher alcohol synthesis reaction as described in Ziegler's U.S. Pat.No. 2,892,858, hereinafter referred to as a “Ziegler alumina”. Ziegleralumina is presently available from the Vista Chemical Company under thetrademark “Catapal” or from Condea Chemie GmbH under the trademark“Pural,” and will be available from ALCOA under the trademark “HiQ-20.”This high-purity pseudoboehmite, after calcination at a hightemperature, has been shown to yield a gamma-alumina of extremely highpurity.

The alumina powder can be formed into any desired shape or type ofcarrier material known to those skilled in the art such as spheres,rods, pills, pellets, tablets, granules, extrudates, and like forms bymethods well known to the practitioners of the catalyst material formingart.

The preferred form of the present catalyst support is a sphere, with apreferred diameter of between about 0.7 mm and 3.5 mm. Alumina spheresmay be continuously manufactured by the well known oil-drop method whichcomprises: forming an alumina hydrosol by any of the techniques taughtin the art and preferably by reacting aluminum metal with hydrochloricacid; combining the resulting hydrosol with a suitable gelling agent;and dropping the resultant mixture into an oil bath maintained atelevated temperatures. The droplets of the mixture remain in the oilbath until they set and form hydrogel spheres. The spheres are thencontinuously withdrawn from the oil bath and typically subjected tospecific aging and drying treatments in oil and an ammoniacal solutionto further improve their physical characteristics. The resulting agedand gelled particles are then washed and dried at a relatively lowtemperature of about 150° to about 205° C. and subjected to acalcination procedure at a temperature of about 450° to about 700° C.for a period of about 1 to about 20 hours. This treatment effectsconversion of the alumina hydrogel to the corresponding crystallinegamma-alumina. U.S. Pat. No. 2,620,314 provides additional details andis incorporated herein by reference thereto.

An alternative form of carrier material is a cylindrical extrudate,preferably prepared by mixing the alumina powder with water and suitablepeptizing agents such as HCl until an extrudable dough is formed. Theamount of water added to form the dough is typically sufficient to givea loss on ignition (LOI) at 500° C. of about 45 to 65 mass-%, with avalue of 55 mass-% being preferred. The acid addition rate is generallysufficient to provide 2 to 7 mass-% of the volatile-free alumina powderused in the mix, with a value of 3 to 4 mass-% being preferred. Theresulting dough is extruded through a suitably sized die to formextrudate particles. These particles are then dried at a temperature ofabout 260° to about 427° C. for a period of about 0.1 to 5 hours to formthe extrudate particles. The preferred diameter of cylindrical extrudateparticles is between about 0.7 and 3.5 mm, with a length-to-diameterratio of between about 1:1 and 5:1.

A platinum-group metal component is an essential ingredient of thecatalyst. This component comprises platinum, palladium, ruthenium,rhodium, iridium, osmium or mixtures thereof, with platinum beingpreferred. The platinum-group metal may exist within the final catalyticcomposite as a compound such as an oxide, sulfide, halide, oxyhalide,etc., in chemical combination with one or more of the other ingredientsof the composite or as an elemental metal. Best results are obtainedwhen substantially all of this component is present in the elementalstate and it is homogeneously dispersed within the carrier material.This component may be present in the final catalyst composite in anyamount which is catalytically effective; the platinum-group metalgenerally will comprise about 0.01 to about 2 mass-% of the finalcatalytic composite, calculated on an elemental basis. Excellent resultsare obtained when the catalyst contains about 0.05 to about 1 mass-% ofplatinum.

The platinum-group metal component may be incorporated in the porouscarrier material in any suitable manner, such as coprecipitation,ion-exchange or impregnation. The preferred method of preparing thecatalyst involves the utilization of a soluble, decomposable compound ofplatinum-group metal to impregnate the carrier material in a relativelyuniform manner. For example, the component may be added to the supportby commingling the latter with an aqueous solution of chloroplatinic orchloroiridic or chloropalladic acid. Other water-soluble compounds orcomplexes of platinum-group metals may be employed in impregnatingsolutions and include ammonium chloroplatinate, bromoplatinic acid,platinum trichloride, platinum tetrachloride hydrate, platinumdichlorocarbonyl dichloride, dinitrodiaminoplatinum, sodiumtetranitroplatinate (II), palladium chloride, palladium nitrate,palladium sulfate, diaminepalladium (II) hydroxide, tetraaminepalladium(II) chloride, hexaminerhodium chloride, rhodium carbonylchloride,rhodium trichloride hydrate, rhodium nitrate, sodium hexachlororhodate(III), sodium hexanitrorhodate (III), iridium tribromide, iridiumdichloride, iridium tetrachloride, sodium hexanitroiridate (III),potassium or sodium chloroiridate, potassium rhodium oxalate, etc. Theutilization of a platinum, iridium, rhodium, or palladium chloridecompound, such as chloroplatinic, chloroiridic or chloropalladic acid orrhodium trichloride hydrate, is preferred since it facilitates theincorporation of both the platinum-group-metal component and at least aminor quantity of the preferred halogen component in a single step.Hydrogen chloride or the like acid is also generally added to theimpregnation solution in order to further facilitate the incorporationof the halogen component and the uniform distribution of the metalliccomponents throughout the carrier material. In addition, it is generallypreferred to impregnate the carrier material after it has been calcinedin order to minimize the risk of washing away the valuableplatinum-group metal.

Generally the platinum-group metal component is dispersed homogeneouslyin the catalyst. Dispersion of the platinum-group metal preferably isdetermined by Scanning Transmission Electron Microscope (STEM),comparing metals concentrations with overall catalyst metal content. Inan alternative embodiment one or more platinum-group metal componentsmay be present as a surface-layer component as described in U.S. Pat.No. 4,677,094, incorporated by reference. The “surface layer” is thelayer of a catalyst particle adjacent to the surface of the particle,and the concentration of surface-layer metal tapers off in progressingfrom the surface to the center of the catalyst particle.

A Group IVA(IUPAC 14) metal component is another essential ingredient ofthe catalyst of the present invention. Of the Group IVA(IUPAC 14)metals, germanium and tin are preferred and tin is especially preferred.This component may be present as an elemental metal, as a chemicalcompound such as the oxide, sulfide, halide, oxychloride, etc., or as aphysical or chemical combination with the porous carrier material and/orother components of the catalytic composite. Preferably, a substantialportion of the Group IVA(IUPAC 14) metal exists in the finished catalystin an oxidation state above that of the elemental metal. The GroupIVA(IUPAC 14) metal component optimally is utilized in an amountsufficient to result in a final catalytic composite containing about0.01 to about 5 mass % metal, calculated on an elemental basis, withbest results obtained at a level of about 0.1 to about 2 mass-% metal.

The Group IVA(IUPAC 14) metal component may be incorporated in thecatalyst in any suitable manner to achieve a homogeneous dispersion,such as by coprecipitation with the porous carrier material,ion-exchange with the carrier material or impregnation of the carriermaterial at any stage in the preparation. One method of incorporatingthe Group IVA(IUPAC 14) metal component into the catalyst compositeinvolves the utilization of a soluble, decomposable compound of a GroupIVA(IUPAC 14) metal to impregnate and disperse the metal throughout theporous carrier material. The Group IVA(IUPAC 14) metal component can beimpregnated either prior to, simultaneously with, or after the othercomponents are added to the carrier material. Thus, the Group IVA(IUPAC14) metal component may be added to the carrier material by comminglingthe latter with an aqueous solution of a suitable metal salt or solublecompound such as stannous bromide, stannous chloride, stannic chloride,stannic chloride pentahydrate; or germanium oxide, germaniumtetraethoxide, germanium tetrachloride; or lead nitrate, lead acetate,lead chlorate and the like compounds. The utilization of Group IVA(IUPAC14) metal chloride compounds, such as stannic chloride, germaniumtetrachloride or lead chlorate is particularly preferred since itfacilitates the incorporation of both the metal component and at least aminor amount of the preferred halogen component in a single step. Whencombined with hydrogen chloride during the especially preferred aluminapeptization step described hereinabove, a homogeneous dispersion of theGroup IVA(IUPAC 14) metal component is obtained in accordance with thepresent invention. In an alternative embodiment, organic metal compoundssuch as trimethyl tin chloride and dimethyl tin dichloride areincorporated into the catalyst during the peptization of the inorganicoxide binder, and most preferably during peptization of alumina withhydrogen chloride or nitric acid.

Indium is another essential component of the present catalyst. Theindium may be present in the catalytic composite in any catalyticallyavailable form such as the elemental metal, a compound such as theoxide, hydroxide, halide, oxyhalide, aluminate, or in chemicalcombination with one or more of the other ingredients of the catalyst.Although not intended to so restrict the present invention, it isbelieved that best results are obtained when the indium is present inthe composite in a form wherein substantially all of the indium moietyis in an oxidation state above that of the elemental metal such as inthe form of the oxide, oxyhalide or halide or in a mixture thereof andthe subsequently described oxidation and reduction steps that arepreferably used in the preparation of the instant catalytic compositeare specifically designed to achieve this end.

Indium can be present in the catalyst in any amount which iscatalytically effective, with good results obtained with about 0.1 toabout 5 mass-% indium on an elemental basis in the catalyst. Bestresults are ordinarily achieved with about 0.2 to about 2 mass-% indium,especially about 0.2 to 1 mass-%, calculated on an elemental basis. Thepreferred atomic ratio of indium to platinum-group metal for thiscatalyst is at least about 1.2:1, preferably about 1.5:1 or more, andoptionally about 2:1 or more; in one embodiment, the ratio is betweenabout 1.2 and 2.5. The relationship of indium to lanthanide in thepresent catalyst is discussed hereinbelow.

An indium component is incorporated in the catalytic composite in anysuitable manner known to the art, such as by coprecipitation, cogelationor coextrusion with the porous carrier material, ion exchange with thegelled carrier material, or impregnation of the porous carrier materialeither after, before, or during the period when it is dried andcalcined. It is intended to include within the scope of the presentinvention all conventional methods for incorporating and simultaneouslydistributing a metallic component in a catalytic composite in a desiredmanner, as the particular method of incorporation used is not deemed tobe an essential feature of the present invention. Preferably the methodused results in a relatively uniform dispersion of the indium moiety inthe carrier material.

One suitable method of incorporating indium into the catalytic compositeinvolves cogelling or coprecipitating the indium component in the formof the corresponding hydrous oxide or oxyhalide during the preparationof the preferred carrier material, alumina. This method typicallyinvolves the addition of a suitable sol-soluble or sol-dispersibleindium compound such as the indium trichloride, indium oxide, and thelike to the alumina hydrosol and then combining the indium-containinghydrosol with a suitable gelling agent and dropping the resultingmixture into an oil bath, etc., as explained in. detail hereinbefore.Alternatively, the indium compound can be added to the gelling agent.After drying and calcining the resulting gelled carrier material in air,an intimate combination of alumina and indium oxide and/or oxychlorideis obtained.

Another effective method of incorporating the indium into the catalyticcomposite involves utilization of a soluble, decomposable compound ofindium in solution to impregnate the porous carrier material. Ingeneral, the solvent used in this impregnation step is selected on thebasis of the capability to dissolve the desired indium compound and tohold it in solution until it is evenly distributed throughout thecarrier material without adversely affecting the carrier material or theother ingredients of the catalyst. Suitable solvents comprise alcohols,ethers, acids, and the like, with an aqueous, acidic solution beingpreferred. Thus, the indium component may be added to the carriermaterial by commingling the carrier with an aqueous acidic solution ofsuitable indium salt, complex, or compound such as a nitrate, chloride,fluoride, organic alkyl, hydroxide, oxide, and the like compounds.Suitable acids for use in the impregnation solution are: inorganic acidssuch as hydrochloric acid, nitric acid, and the like, and stronglyacidic organic acids such as oxalic acid, malonic acid, citric acid, andthe like. The indium component can be impregnated into the carriereither prior to, simultaneously with, or after the platinum-group metalcomponent.

A lanthanide-series metal is another essential component of the presentcatalyst. Included in the lanthanide series are lanthanum, cerium,praseodymium, neodymium, promethium, samarium, europium, gadolinium,terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium; acerium component is preferred. The lanthanide component may in generalbe present in the catalytic composite in any catalytically availableform such as the elemental metal, a compound such as the oxide,hydroxide, halide, oxyhalide, aluminate, or in chemical combination withone or more of the other ingredients of the catalyst. Although notintended to so restrict the present invention, it is believed that bestresults are obtained when the lanthanide component is present in thecomposite in a form wherein substantially all of the lanthanide moietyis in an oxidation state above that of the elemental metal such as inthe form of the oxide, oxyhalide or halide or in a mixture thereof andthe subsequently described oxidation and reduction steps that arepreferably used in the preparation of the instant catalytic compositeare specifically designed to achieve this end.

The lanthanide-metal component is incorporated into the catalyst in anyamount which is catalytically effective, with good results obtained withabout 0.05 to about 5 mass-% lanthanide on an elemental basis in thecatalyst. Best results are ordinarily achieved with about 0.2 to about 2mass-% lanthanide, calculated on an elemental basis. The preferredatomic ratio of lanthanide to platinum-group metal for this catalyst isat least about 1.3:1, preferably about 1.5:1 or more, and especiallyfrom about 2:1 to about 5:1. The relationship of lanthanide to indium inthe present catalyst is discussed hereinbelow.

The lanthanide component is incorporated in the catalytic composite inany suitable manner known to the art, such as by coprecipitation,cogelation or coextrusion with the porous carrier material, ion exchangewith the gelled carrier material, or impregnation of the porous carriermaterial either after, before, or during the period when it is dried andcalcined. It is intended to include within the scope of the presentinvention all conventional methods for incorporating and simultaneouslydistributing a metallic component in a catalytic composite in a desiredmanner, as the particular method of incorporation used is not deemed tobe an essential feature of the present invention. Preferably the methodused results in a relatively uniform dispersion of the lanthanide moietyin the carrier material, although methods which result in non-uniformlanthanide distribution are within the scope of the present invention.

One suitable method of incorporating the lanthanide component into thecatalytic composite involves cogelling or coprecipitating the lanthanidecomponent in the form of the corresponding hydrous oxide or oxyhalideduring the preparation of the preferred carrier material, alumina. Thismethod typically involves the addition of a suitable sol-soluble orsol-dispersible lanthanide compound such as the lanthanide trichloride,lanthanide oxide, and the like to the alumina hydrosol and thencombining the lanthanide-containing hydrosol with a suitable gellingagent and dropping the resulting mixture into an oil bath, etc., asexplained in detail hereinbefore. Alternatively, the lanthanide compoundcan be added to the gelling agent. After drying and calcining theresulting gelled carrier material in air, an intimate combination ofalumina and lanthanide oxide and/or oxychloride is obtained.

One preferred method of incorporating the lanthanide-series metalcomponent into the catalytic composite involves utilization of asoluble, decomposable compound of lanthanide in solution to impregnatethe porous carrier material. In general, the solvent used in thisimpregnation step is selected on the basis of the capability to dissolvethe desired lanthanide compound and to hold it in solution until it isevenly distributed throughout the carrier material without adverselyaffecting the carrier material or the other ingredients of the catalyst.Suitable solvents comprise alcohols, ethers, acids, and the like, withan aqueous, acidic solution being preferred. Thus, the lanthanidecomponent may be added to the carrier material by commingling thecarrier with an aqueous acidic solution of suitable lanthanide salt,complex, or compound such as a nitrate, chloride, fluoride, organicalkyl, hydroxide, oxide, and the like compounds. Suitable acids for usein the impregnation solution are: inorganic acids such as hydrochloricacid, nitric acid, and the like, and strongly acidic organic acids suchas oxalic acid, malonic acid, citric acid, and the like. The lanthanidecomponent can be impregnated into the carrier either prior to,simultaneously with, or after the platinum-group metal component.

As an alternative to a uniform distribution of one or more of the abovemetals in the carrier, a surface-layer metal may be incorporated intothe catalyst particle in any manner suitable to effect a decreasinggradient of the metal from the surface to the center of the particle.Preferably, the metal is impregnated into the support as a compoundwhich decomposes upon contact with the carrier, releasing the metal ator near the surface of the particle. Other means, which do not limit theinvention, include using a compound of the metal which complexes withthe carrier or which does not penetrate into the interior of theparticle. An example is a multi-dentated ligand, such as carboxylicacids or metal compounds containing amino groups, thiol groups,phosphorus groups or other polar groups which can bond strongly to anoxide support. Alternatively, the metal may be incorporated into thecatalyst by spray impregnation.

Optionally, the catalyst may also contain other components or mixturesthereof which act alone or in concert as catalyst modifiers to improveactivity, selectivity or stability. Some known catalyst modifiersinclude rhenium, cobalt, nickel, iron, tungsten, molybdenum, chromium,bismuth, antimony, zinc, cadmium and copper. Catalytically effectiveamounts of these components may be added in any suitable manner to thecarrier material during or after its preparation or to the catalyticcomposite before, while or after other components are beingincorporated.

Preferably, however, a metal component of the catalyst consistsessentially of a platinum-group metal, a Group IVA(IUPAC 14) metal,indium and a lanthanide-series metal, and more preferably of platinum,tin, indium and cerium. The indium and lanthanide-series metal are tosome extent interchangeable, approximately on an atomic basis, with theatomic ratio of indium to lanthanide being within the range of fromabout 1:20 to 10:1, respectively. The ratio of the total of(indium+lanthanide-series metal) to platinum-group metal is at leastabout 1.5, preferably about 2 or more, and more preferably at leastabout 3 on an atomic basis.

An optional component of the catalyst, useful in hydrocarbon conversionembodiments of the present invention comprising dehydrogenation,dehydrocyclization, or hydrogenation reactions, is an alkali oralkaline-earth metal component. More precisely, this optional ingredientis selected from the group consisting of the compounds of the alkalimetals—cesium, rubidium, potassium, sodium, and lithium—and thecompounds of the alkaline earth metals—calcium, strontium, barium, andmagnesium. Generally, good results are obtained in these embodimentswhen this component constitutes about 0.01 to about 5 mass-% of thecomposite, calculated on an elemental basis. This optional alkali oralkaline earth metal component can be incorporated into the composite inany of the known ways with impregnation with an aqueous solution of asuitable water-soluble, decomposable compound being preferred.

As heretofore indicated, it is necessary to employ at least oneoxidation step in the preparation of the catalyst. The conditionsemployed to effect the oxidation step are selected to convertsubstantially all of the metallic components within the catalyticcomposite to their corresponding oxide form. The oxidation steptypically takes place at a temperature of from about 370° to about 650°C. An oxygen atmosphere is employed typically comprising air. Generally,the oxidation step will be carried out for a period of from about 0.5 toabout 10 hours or more, the exact period of time being that required toconvert substantially all of the metallic components to theircorresponding oxide form. This time will, of course, vary with theoxidation temperature employed and the oxygen content of the atmosphereemployed.

In addition to the oxidation step, a halogen adjustment step may also beemployed in preparing the catalyst. As heretofore indicated, the halogenadjustment step may serve a dual function. First, the halogen adjustmentstep may aid in homogeneous dispersion of the Group IVA(IUPAC 14) metaland other metal component. Additionally, the halogen adjustment step canserve as a means of incorporating the desired level of halogen into thefinal catalytic composite. The halogen adjustment step employs a halogenor halogen-containing compound in air or an oxygen atmosphere. Since thepreferred halogen for incorporation into the catalytic compositecomprises chlorine, the preferred halogen or halogen-containing compoundutilized during the halogen adjustment step is chlorine, HCl orprecursor of these compounds. In carrying out the halogen adjustmentstep, the catalytic composite is contacted with the halogen orhalogen-containing compound in air or an oxygen atmosphere at anelevated temperature of from about 370° to about 650° C. It is furtherdesired to have water present during the contacting step in order to aidin the adjustment. In particular, when the halogen component of thecatalyst comprises chlorine, it is preferred to use a mole ratio ofwater to HCl of about 5:1 to about 100:1. The duration of thehalogenation step is typically from about 0.5 to about 5 hours or more.Because of the similarity of conditions, the halogen adjustment step maytake place during the oxidation step. Alternatively, the halogenadjustment step may be performed before or after the oxidation step asrequired by the particular method being employed to prepare the catalystof the invention. Irrespective of the exact halogen adjustment stepemployed, the halogen content of the final catalyst should be such thatthere is sufficient halogen to comprise, on an elemental basis, fromabout 0.1 to about 10 mass-% of the finished composite.

In preparing the catalyst, it is also necessary to employ a reductionstep. The reduction step is designed to reduce substantially all of theplatinum-group metal component to the corresponding elemental metallicstate and to ensure a relatively uniform and finely divided dispersionof this component throughout the refractory inorganic oxide. It ispreferred that the reduction step take place in a substantiallywater-free environment. Preferably, the reducing gas is substantiallypure, dry hydrogen (i.e., less than 20 volume ppm water). However, otherreducing gases may be employed such as CO, nitrogen, etc. Typically, thereducing gas is contacted with the oxidized catalytic composite atconditions including a reduction temperature of from about 315° to about650° C. for a period of time of from about 0.5 to 10 or more hourseffective to reduce substantially all of the platinum-group metalcomponent to the elemental metallic state.

The reduction step may be performed prior to loading the catalyticcomposite into the hydrocarbon conversion zone or it may be performed insitu as part of a hydrocarbon conversion process start-up procedure.However, if this latter technique is employed, proper precautions mustbe taken to predry the conversion unit to a substantially water-freestate, and a substantially water-free reducing gas should be employed.

Optionally, the catalytic composite may be subjected to a presulfidingstep. The optional sulfur component may be incorporated into thecatalyst by any known technique.

The catalyst of the present invention has particular utility as ahydrocarbon conversion catalyst. The hydrocarbon which is to beconverted is contacted with the catalyst at hydrocarbon-conversionconditions, which include a temperature of from 40° to 300° C., apressure of from atmospheric to 200 atmospheres absolute and liquidhourly space velocities from about 0.1 to 100 hr⁻¹. The catalyst isparticularly suitable for catalytic reforming of gasoline-rangefeedstocks, and also may be used for, inter alia, dehydrocyclization,isomerization of aliphatics and aromatics, dehydrogenation,hydrocracking, disproportionation, dealkylation, alkylation,transalkylation, and oligomerization.

In the preferred catalytic reforming embodiment, hydrocarbon feedstockand a hydrogen-rich gas are preheated and charged to a reforming zonecontaining typically two to five reactors in series. Suitable heatingmeans are provided between reactors to compensate for the netendothermic heat of reaction in each of the reactors. Reactants maycontact the catalyst in individual reactors in either upflow, downflow,or radial flow fashion, with the radial flow mode being preferred. Thecatalyst is contained in a fixed-bed system or, preferably, in amoving-bed system with associated continuous catalyst regeneration.Alternative approaches to reactivation of deactivated catalyst are wellknown to those skilled in the art, and include semi-regenerativeoperation in which the entire unit is shut down for catalystregeneration and reactivation or swing-reactor operation in which anindividual reactor is isolated from the system, regenerated andreactivated while the other reactors remain on-stream. The preferredcontinuous catalyst regeneration in conjunction with a moving-bed systemis disclosed, inter alia, in U.S. Pat. Nos. 3,647,680; 3,652,231;3,692,496; and 4,832,291, all of which are incorporated herein byreference.

Effluent from the reforming zone is passed through a cooling means to aseparation zone, typically maintained at about 0° to 65° C., wherein ahydrogen-rich gas is separated from a liquid stream commonly called“unstabilized reformate”. The resultant hydrogen stream can then berecycled through suitable compressing means back to the reforming zone.The liquid phase from the separation zone is typically withdrawn andprocessed in a fractionating system in order to adjust the butaneconcentration, thereby controlling front-end volatility of the resultingreformate.

Reforming conditions applied in the reforming process of the presentinvention include a pressure selected within the range of about 100 kPato 7 MPa (abs). Particularly good results are obtained at low pressure,namely a pressure of about 350 to 2500 kPa (abs). Reforming temperatureis in the range from about 315° to 600° C., and preferably from about425° to 565° C. As is well known to those skilled in the reforming art,the initial selection of the temperature within this broad range is madeprimarily as a function of the desired octane of the product reformateconsidering the characteristics of the charge stock and of the catalyst.Ordinarily, the temperature then is thereafter slowly increased duringthe run to compensate for the inevitable deactivation that occurs toprovide a constant octane product. Sufficient hydrogen is supplied toprovide an amount of about 1 to about 20 moles of hydrogen per mole ofhydrocarbon feed entering the reforming zone, with excellent resultsbeing obtained when about 2 to about 10 moles of hydrogen are used permole of hydrocarbon feed. Likewise, the liquid hourly space velocity(LHSV) used in reforming is selected from the range of about 0.1 toabout 20 hr⁻¹, with a value in the range of about 1 to about 5 hr⁻¹being preferred.

The hydrocarbon feedstock that is charged to this reforming systempreferably is a naphtha feedstock comprising naphthenes and paraffinsthat boil within the gasoline range. The preferred feedstocks arenaphthas consisting principally of naphthenes and paraffins, although,in many cases, aromatics also will be present. This preferred classincludes straight-run gasolines, natural gasolines, synthetic gasolines,and the like. As an alternative embodiment, it is frequentlyadvantageous to charge thermally or catalytically cracked gasolines,partially reformed naphthas, or dehydrogenated naphthas. Mixtures ofstraight-run and cracked gasoline-range naphthas can also be used toadvantage. The gasoline-range naphtha charge stock may be a full-boilinggasoline having an initial ASTM D-86 boiling point of from about 40-80°C. and an end boiling point within the range of from about 160-220° C.,or may be a selected fraction thereof which generally will be ahigher-boiling fraction commonly referred to as a heavy naphtha—forexample, a naphtha boiling in the range of 100-200° C. If the reformingis directed to production of one or more of benzene, toluene andxylenes, the boiling range may be principally or substantially withinthe range of 60-150° C. In some cases, it is also advantageous toprocess pure hydrocarbons or mixtures of hydrocarbons that have beenrecovered from extraction units—for example, raffinates from aromaticsextraction or straight-chain paraffins—which are to be converted toaromatics.

It is generally preferred to utilize the present invention in asubstantially water-free environment. Essential to the achievement ofthis condition in the reforming zone is the control of the water levelpresent in the.feedstock and the hydrogen stream which is being chargedto the zone. Best results are ordinarily obtained when the total amountof water. entering the conversion zone from any source is held to alevel less than 50 ppm and preferably less than 20 ppm, expressed asweight of equivalent water in the feedstock. In general, this can beaccomplished by careful control of the water present in the feedstockand in the hydrogen stream. The feedstock can be dried by using anysuitable drying means known to the art such as a conventional solidadsorbent having a high selectivity for water; for instance, sodium orcalcium crystalline aluminosilicates, silica gel, activated alumina,molecular sieves, anhydrous calcium sulfate, high surface area sodium,and the like adsorbents. Similarly, the water content of the feedstockmay be adjusted by suitable stripping operations in a fractionationcolumn or like device. In some cases, a combination of adsorbent dryingand distillation drying may be used advantageously to effect almostcomplete removal of water from the feedstock. Preferably, the feedstockis dried to a level corresponding to less than 20 ppm of H₂O equivalent.

It is preferred to maintain the water content of the hydrogen streamentering the hydrocarbon conversion zone. at a level of about 10 toabout 20 volume ppm or less. In the cases where the water content of thehydrogen stream is above this range, this can be convenientlyaccomplished by contacting the hydrogen stream with a suitable desiccantsuch as those mentioned above at conventional drying conditions.

It is a preferred practice to use the present invention in asubstantially sulfur-free environment. Any control means known in theart may be used to treat the naphtha feedstock which is to be charged tothe reforming reaction zone. For example, the feedstock may be subjectedto adsorption processes, catalytic processes, or combinations thereof.Adsorption processes may employ molecular sieves, high surface areasilica-aluminas, carbon molecular sieves, crystalline aluminosilicates,activated carbons, high surface area metallic containing compositions,such as nickel or copper and the like. It is preferred that thesefeedstocks be treated by conventional catalytic pre-treatment methodssuch as hydrorefining, hydrotreating, hydrodesulfurization, etc., toremove substantially all sulfurous, nitrogenous and water-yieldingcontaminants therefrom, and to saturate any olefins that may becontained therein. Catalytic processes may employ traditional sulfurreducing catalyst formulations known to the art including refractoryinorganic oxide supports containing metals selected from the groupcomprising Group VI-B(6), Group II-B(12), and Group VIII(IUPAC 8-10) ofthe Periodic Table.

One embodiment of the invention involves the process of converting anaphtha feedstock at catalytic dehydrocyclization conditions. Inparticular, the preferred naphtha feedstock comprises C₆-C₈ non-aromatichydrocarbons. Dehydrocyclization conditions include a pressure of fromabout 100 kPa to 4 MPa (abs), with the preferred pressure being fromabout 200 kPa to 1.5 MPa, a temperature of from about 350° to 650° C.,and a liquid hourly space velocity of from about 0.1 to about 10 hr⁻¹.Preferably, hydrogen may be employed as a diluent. When present,hydrogen may be circulated at a rate of from about 0.2 to about 10 molesof hydrogen per mole of feedstock hydrocarbon. It is preferred that thenaphtha feedstock of the alternative dehydrocyclization processembodiment comprises a high proportion of paraffins, as the purpose of adehydrocyclization process is to convert paraffins to aromatics. Becauseof the high value of C₆-C₈ aromatics, it is additionally preferred thatthe naphtha feedstock comprise C₆-C₈ paraffins. However, notwithstandingthis preference, the naphtha feedstock may comprise naphthenes,aromatics, and olefins in addition to C₆-C₈ paraffins.

EXAMPLES

The following examples are presented to elucidate the catalyst andprocess of the present invention, demonstrating selectivity advantagesover prior-art technology. These examples are offered as illustrativeembodiments and should not be interpreted as limiting the claims.

The feedstock used in all but Example VI of the tests ofreforming-catalyst performance consisted essentially of 90 mass-% normalheptane (n-heptane) and 10 mass-% orthoxylene. Example VI used analternative naphtha feedstock described in that section below.

Example I

Two spherical catalysts of the prior art comprising platinum, tin andindium on alumina were prepared by conventional techniques as controlsrelative to the invention. Tin was incorporated into alumina solaccording to the prior art, and the tin-containing alumina sol wasoil-dropped to form 1.6 mm spheres which were steamed to dryness atabout 10% LOI and calcined at 650° C. The spherical supports then wereco-impregnated with indium chloride and chloroplatinic acid in 3% HCl.The impregnated catalysts were dried and oxychlorinated at 525° C. with2M HCl in air and reduced with pure hydrogen at 565° C.

The finished controls were designated respectively Catalysts A, B, andD, and each contained about 1.3 mass-% chloride and had the followingapproximate metals contents as mass-% of the elemental metal:

Catalyst: A B D Platinum 0.38 0.36 0.29 Tin 0.3  0.3  0.3  Indium 0.391.14 0.56

Example II

A spherical catalyst comprising platinum, tin and cerium on alumina wasprepared as a control relative to the invention. Tin was incorporatedinto a spherical alumina support according to the prior art as describedin Example I. The spherical support then was impregnated with ceriumnitrate in 3.5% nitric acid at a solution-to-support ratio of 1:1. Theresulting composite was steamed to dryness (˜10% LOI) and calcined at650° C. with 3% steam. The resulting calcined composite was impregnatedwith chloroplatinic acid in HCl to provide 0.38 mass-% Pt in thefinished catalyst. The impregnated catalyst was dried and oxychlorinatedat 525° C. with 2M HCl in air and reduced with pure H₂ at 565° C. Thefinished Ce-containing catalyst was designated as Catalyst C, containedabout 1.4 mass-% chloride and had the following approximate metalscontents as mass-% of the elemental metal:

Platinum 0.37 Tin 0.3  Cerium 0.96

Example III

A spherical catalyst comprising platinum, tin, indium and cerium onalumina was prepared to demonstrate the features of the invention. Tinwas incorporated into a spherical alumina support according to the priorart as described in Example I. The spherical support then wasco-impregnated with indium chloride, cerium nitrate and chloroplatinicacid in 3% HCl. The impregnated catalyst was dried and oxychlorinated at525° C. with 2M HCl in air and reduced with pure H₂ at 565° C. Thefinished In- and Ce-containing catalyst was designated as Catalyst X,contained about 1.4 mass-% chloride and had the following approximatemetals contents as mass-% of the elemental metal:

Platinum 0.37 Tin 0.3  Indium 0.40 Cerium 1.00

Example IV

Pilot plant tests were structured to compare the selectivity andactivity of control Catalysts A, B and C with that of Catalyst X of theinvention for the catalytic reforming of a feedstock as describedhereinabove.

Each test was based on reforming conditions comprising a pressure of 0.8MPa (abs), a mass hourly space velocity of 3 hr⁻¹, and ahydrogen/hydrocarbon ratio of 8. A range of conversion was studied byvarying temperature to provide several data points each at 470° C., 480°C., 490° C., and 500° C.

Conversion of heptanes over the four catalysts is compared in FIG. 1 asa function of the above range of temperatures. Catalyst X of theinvention demonstrated conversions intermediate between the high-indiumand the low-indium and cerium-containing control catalysts.

FIG. 2 shows mass-% selectivity to aromatics based on 25% heptanesconversion. Catalyst X of the invention demonstrated about 1½% higherselectivity to aromatics than the best of the control catalysts.

Thus, the catalyst of the invention combines higher activity thanhigh-indium catalyst of the art with the highest selectivity of any ofthe catalysts tested.

Example V

A spherical catalyst comprising platinum, germanium, indium andlanthanum on alumina was prepared to demonstrate another aspect of thefeatures of the invention. A spherical alumina support wasco-impregnated with indium chloride, lanthanum nitrate, germaniumchloride and chloroplatinic acid in 3% HCl. The impregnated catalyst wasdried and oxychlorinated at 525° C. with 2M HCl in air and reduced withpure H₂ at 565° C. The finished Ge-, In-, and La-containing catalyst wasdesignated as Catalyst Y, contained about 1.3 mass-% chloride and hadthe following approximate metals contents as mass-% of the elementalmetal:

Platinum 0.28 Germanium 0.23 Indium 0.39 Lanthanum 0.95

Example VI

Additional pilot plant tests were structured to compare the selectivityand activity of control Catalyst D with that of Catalyst Y of theinvention for the catalytic reforming of a hydrotreatedpetroleum-derived naphtha derived from a paraffinic mid-continent crudeoil which had the following characteristics:

Specific Gravity 0.737 Distillation, ASTM D-86, ° C. IBP 84 10% 102 50%121 90% 144 EP 164 Mass % paraffins 57 naphthenes 29 aromatics 14

Each test was based on reforming conditions comprising a pressure of 0.8MPa (abs), a mass hourly space velocity of 2 hr⁻¹, and ahydrogen/hydrocarbon ratio of 3.3. A range of conversion was studied byvarying temperature to provide several data points each at 490° C., 500°C., 510° C., and 520° C.

Conversion over the two catalysts is compared in FIG. 3 as a function ofthe above range of temperatures. Catalyst Y of the inventiondemonstrated conversions similar to the control catalyst D.

FIG. 4 shows mass-% selectivity to aromatics based on about 82%paraffin+naphthene conversion. Catalyst Y of the invention demonstratedabout 1½% higher selectivity to aromatics the control catalyst, whichindicated that the alternate embodiment of the invention performedsimilarly to Catalyst X in displaying improved selectivity for theconversion of naphtha feedstock.

I claim as my invention:
 1. A catalytic composite having enhancedconversion of paraffins to aromatics during reforming of a naphthafeedstock consisting essentially of a combination of a refractoryinorganic oxide support with from about 0.1 to 10 mass-% on an elementalbasis of a halogen component, about 0.01 to 2 mass-% on an elementalbasis of a platinum component, about 0.01 to 5 mass-% on an elementalbasis of a Group IVA (IUPAC 14) metal component selected from the groupconsisting of tin and germanium, about 0.1 to 5 mass-% on an elementalbasis of an indium component and about 0.05 to 5 mass-% on an elementalbasis of a lanthanide-series metal component selected from the groupconsisting of cerium and lanthanum.
 2. The catalytic composite of claim1 wherein the refractory inorganic oxide is alumina.
 3. The catalyticcomposite of claim 1 wherein the Group IVA(IUPAC 14) metal component isa tin component.
 4. The catalytic composite of claim 1 wherein the GroupIVA(IUPAC 14) metal component is a germanium component.
 5. The catalyticcomposite of claim 1 wherein the lanthanide-series metal component is alanthanum component.
 6. The catalytic composite of claim 1 wherein thelanthanide-series metal component is a cerium component.
 7. Thecatalytic composite of claim 1 wherein the atomic ratio oflanthanide-series metal to platinum metal is at least about 1.3.
 8. Thecatalytic composite of claim 1 wherein the atomic ratio of(indium+lanthanide-series metal) to platinum metal is at least about1.5.
 9. The catalytic composite of claim 1 wherein the atomic ratio ofindium to lanthanide-series metal is within the range of from about 1:20to 10:1.
 10. The catalytic composite of claim 1 wherein the halogencomponent is a chlorine component.
 11. A catalytic composite comprisinga combination of a halogenated alumina support with a metal componentconsisting essentially of about 0.01 to 2 mass-% on an elemental basisof a platinum component, about 0.01 to 5 mass-% on an elemental basis ofa germanium component, about 0.1 to 5 mass-% on an elemental basis of anindium component and about 0.05 to 5 mass-% on an elemental basis of alanthanum component.